This invention relates to a portable information device such as a portable telephone, a personal computer notebooks, a personal digital assistant (PDA) and a VTR camera, as well as a charger for such a device. More particularly, this invention relates to the system structure for setting time information easily for the main part of such a portable information device.
Information devices, such as personal computers, generally manage data by attaching time information such as time and date to different kinds of data and by taking into consideration the age of each data item. For the same reason, portable information devices of the kind described above having a clock function are also adapted to carry out data management by attaching time information to each data item, having, in addition to a main battery, a backup battery for the semiconductor memory such as an SRAM or an auxiliary battery for the clock such that data maintenance and continuous operation of the clock function can be carried out even when the main battery serving as the power source of the device is being exchanged or the source voltage of the main battery has dropped below the level of the action voltage.
Many of more recent portable information devices now use a non-volatile semiconductor memory (herein referred to simply as "non-volatile memory"), such as FLASH and FRAM, that does not require a backup battery, but an auxiliary battery for a watch is used for the sole purpose of continuously carrying out its clocking operation. It now goes without saying that it is desirable to make portable devices as compact as possible. Since a smaller device means a smaller space inside its housing, there has been a strong desire to do away with an auxiliary battery, if possible.
In practice, however, auxiliary batteries could not be dispensed with because, if the auxiliary battery is taken away from a portable information device having a clock function, the clocking operation will be stopped with an error introduced into the time information when, for example, the main battery is exchanged or there is an over-discharge such that the source voltage drops below the operational voltage. Thus, the time information will have to be reset after each recovery of the source voltage, say, after the main battery has been exchanged, but portable information devices are usually not provided with a switch dedicated to the setting of the clock because their housing is designed to be as compact as possible. This means that the resetting of the clock must be done by sharing a switch for some other purpose, and the user will be required to go through a series of complicated operations which are difficult to understand and cumbersome to carry out.